Exhaust gas recirculation control

ABSTRACT

In an internal combustion engine, exhaust gas is recirculated from the intake manifold exhaust gas crossover passage to the induction passage. An exhaust gas recirculation control valve is positioned by the throttle to proportion exhaust gas recirculation flow to induction airflow. In one embodiment, the exhaust gas recirculation passages are cast integrally in the intake manifold. Fuel metering in a timed fuel injection system responsive to manifold absolute pressure is compensated for exhaust gas recirculation.

United States Patent lnventor Francis A. Sciabica Pentield, N.Y.

Appl. No. 39,663

Filed May 22, 1970 Patented Oct. 5, 1 971 Assignee General MotorsCorporation Detroit, Mich.

EXHAUST GAS RECIRCULATION CONTROL 2 Claims, 10 Drawing Figs.

US. Cl 123/119 A, 123/32 EA,123/139 AW Int. Cl F02n 25/06 Field ofSearch 123/119 A, 119, 139 AW, 32 EA References Cited UNITED STATESPATENTS 3,203,410 8/1965 Scholl 123/32 EA 5/1969 Sarto et al 123/119 A3,457,906 7/1969 Daigh l23/l l9 A 3,464,396 9/1969 Scholl 123/32 EA3,465,736 9/1969 Daigh et al. l23/l 19A 3,470,857 10/1969 Stivenderl23/l 19 A Primary ExaminerWendell E. Burns Attorneys-J. L. Carpenterand C. K. Veenstra ABSTRACT: In an internal combustion engine, exhaustgas is recirculated from the intake manifold exhaust gas crossoverpassage to the induction passage. An exhaust gas recirculation controlvalve is positioned by the throttle to proportion exhaust gasrecirculation flow to induction airflow. In one embodiment, the exhaustgas recirculation passages are cast integrally in the intake manifold.Fuel metering in a timed fuel injection system responsive to manifoldabsolute pressure is compensated for exhaust gas recirculation.

PATENTED mm 5 |97| SHEET 3 [1F 4 ATTORNEY EXHAUST GAS RECIRCULATIONCONTROL This invention provides a control mechanism for an exhaust gasrecirculation system. In this system, an exhaust gas recirculationcontrol valve is positioned by the throttle through a linearly movablecam member which permits ready visualization and calculation of theposition of the control valve. Thus the position of the control valvemay be easily adjusted relative to the position of the throttle so thatexhaust gas recirculation flow may be properly proportioned to inductionairflow.

This invention further provides an exhaust gas recirculation controlmechanism operated by the throttle in which the throttle may return toidle position even if the control valve or cam member were to remain atan intermediate position.

The details as well as other objects and advantages of this inventionare set forth below and shown by the drawings wherein:

FIG. 1 is a top plan view of an induction passage throttle body and anexhaust gas recirculation control valve;

FIG. 2 is a side elevational view of the device shown in FIG. 1illustrating the configuration of the cam member;

FIG. 3 is a sectional view taken along line 33 of FIG. 1 illustratingthe exhaust gas recirculation control valve;

FIG. 4 is a sectional view along line 44 of FIG. 1 illustrating thecontrol valve-operating mechanism;

FIG. 5 is a sectional view along line 55 of FIG. 2 illustrating theadjustable connection in the linkage between the exhaust gasrecirculation control valve and the throttle;

FIG. 6 is a top plan view of the FIG. 1 intake manifold illustrating theexhaust gas crossover passage;

FIG. 7 is a top plan view of an alternative intake manifold havingintegrally cast exhaust gas recirculation passages:

FIG. 8 is a sectional view taken along line 8-8 of FIG. 7 illustratingthe openings from the exhaust gas recirculation passage to the inductionpassages;

FIG. 9 is a view similar to FIG. 2 illustrating the fuel meteringcompensating mechanism; and

FIG. 10 is a circuit diagram for an electronically controlled timed fuelinjection system illustrating two embodiments of variable impedancedevices for compensating the fuel metering.

Referring first to FIGS. 1 and 2, a throttle body assembly 10 is mountedon an intake manifold 12. A pair of induction passages 14 pass throughassembly 10 and are controlled by a pair of throttles 16 disposed on athrottle shaft 18.

Inserted between throttle body assembly 10 and manifold 12 is a plate 20and a base 22 which have extensions of induction passages 14. Plate 20and base 22 define an exhaust gas recirculation inlet passage 24 leadingto a control valve assembly 26 and an exhaust gas recirculation outletpassage 28 leading from control valve assembly 26. Branches 30 connectexhaust gas recirculation outlet passage 28 with induction passages 14below throttles 16. For simplicity, exhaust gas recirculation inletpassage 24 will be referred to merely as exhaust gas recirculationpassage 24, exhaust gas recirculation outlet passage 28 will be referredto as metered exhaust gas passage 28, and the two passages 24 and 28will be referred to collectively as exhaust gas recirculation passages.

As shown in FIG. 3, exhaust gas recirculation control valve assembly 26has an inlet bore 32 leading from exhaust gas recirculation passage 24to an upper cross passage 34. A butterfly valve 36 is disposed on ashaft 38 in an outlet bore 40 leading from cross passage 34 to meteredexhaust gas passage 28.

Shaft 38 is joumaled on a pair of bushings 42 (FIG. 4) and has a lever44 (FIGS. 2 and 4) secured on the outer end thereof. A torsion spring 46(FIG. 4) biases shaft 38 and lever 44 in a counterclockwise direction asviewed in FIG. 2.

The cover 48 for control valve assembly 26 provides a bracket having anupstanding arm 50 (FIGS. 1 and 4) into which a pair of bolts 52 arethreadedly secured. As shown in FIG. 2, bolts 52 extend through a slot54 in a cam member 56, thereby supporting cam member 56 for linearmotion.

An additional bolt 58 also extends through slot 54 and is secured to anadjusting nut 60. Adjusting nut 60 threadedly receives a link 62connected to a throttle lever 64 secured on throttle shaft 18.

A spring 66 biases cam member 56 leftwardly as viewed in FIGS. 1 and 2.

In operation, clockwise opening movement of throttles l6, throttle shaft18 and throttle lever 64 pulls link 62 and cam member 56 toward theright as viewed in FIG. 2. A cam follower 68 on control valve lever 44is biased against a cam surface 70 on cam member 56. As is evident fromFIG. 2, cam follower 68 successively contacts a first portion 700 inwhich control valve 36 remains closed, a first ramp 70b in which controlvalve 36 opens, a peak 700 in which control valve 36 remains open, asecond ramp 70d in which control valve 36 closes, and a second portion702 in which control valve 36 remains closed. The sequence is reversedas throttles 16 are closed and spring 66 returns cam member 56 towardthe left.

Cam surface 70 is configured whereby control valve 36 begins openingmovement when throttles I6 have been opened about 5", reaches a fullyopen position when throttles 16 have been opened between 14 and 20, andreturns to closed position when throttles 16 have been opened about 34.

As control valve 36 opens, exhaust gas received through exhaust gasrecirculation passage 24 is admitted to metered exhaust passage 28 anddelivered through branches 30 to induction passages 14.

It will be noted that since control valve 36 and cam member 56 arebiased in a valve closing direction by springs 46 and 66, they exert noopening force on throttles 16. Moreover, even if control valve 36 or cammember 56 were to remain in an open position, throttles 16 would be freeto close because bolt 58 rides toward the left in slot 54 as throttles16 are closed.

Exhaust gas is received by exhaust gas recirculation passage 24 from anexhaust gas riser bore 72 connecting with an exhaust gas crossoverpassage 74 which passes through intake manifold 12. As may be seen inFIG. 6, intake manifold 12 includes a pair of conventional riserpassages 76 which communicate with generally horizontal upper and lowerplenum chambers 78 and 79 respectively. Plenum chambers 78 and 79 extendlongitudinally from the bottom of riser passages 76 to transverse runnerpassages 80 at the ends thereof. Exhaust crossover passage 74 extendsfrom an inlet 75 at one side of manifold 12, beneath riser passages 76and plenum chambers 78 and 79, to exhaust gas riser bore 72.

It will be appreciated, of course, that induction passages 14, manifoldriser passages 76, plenum chambers 78 and 79, and runner passages 80 maybe collectively referred to as an induction passage.

FIGS. 7 and 8 show a modified intake manifold 12 in which the exhaustgas recirculation and metered exhaust gas passages are cast integrallyin the manifold. The FIG. 7 view is schematic and various combinationsof dot-dash lines have been used to facilitate visualization of thedifferent passages. As shown in these FIGS., a pair of riser passages 76disposed on opposite sides of the manifold center line connect withupper and lower plenum chambers 78 and 79, respectively, which aregenerally horizontal and extend longitudinally through the manifold totransversely reaching runner passages 80.

An exhaust gas crossover passage 74' extends from an inlet 75' at oneside of the manifold center line, beneath riser passages 76 and plenumchambers 78 and 79, to the opposite side of the manifold centerline.There exhaust gas crossover passage 74 discharges into an exhaust gasrecirculation passage 24'. Passage 24' leads to a pad 82 which isadapted to receive control valve assembly 26. Alternatively, an exhaustgas recirculation control valve of different design could be received ina pocket in manifold 12'. A metered exhaust gas passage 28' extends frompad 82, above exhaust gas recirculation passage 24' above exhaust gascrossover passage 74', and under upper plenum chamber 78 to a pair ofports 84 and 86. Port 84 opens vertically into the bottom of upperplenum chamber 78 and is centered below the associated riser passage 76.Port 86 opens horizontally into lower plenum chamber 79.

Thus exhaust gas is recirculated through a crossover passage to heat theinduction passages and is then delivered through a control valveassembly into the induction passages.

It will be noted that all exhaust gas recirculated to the engine isdelivered through the exhaust gas crossover passage to heat theinduction passages, and all exhaust gas delivered through the exhaustgas crossover passage is recirculated to the engine. Thus the exhaustgas recirculation control valve controls both the flow of exhaust gasfor heating the induction passages and the flow of exhaust gasrecirculated to the engine. This combination proves advantageous underconditions such as wide open throttle operation where exhaust gasrecirculation and induction passage heating should be reduced formaximum power. It should be recognized, however, that the advantages ofthis manifold structure are not limited to a system in which all exhaustgas flowing through the exhaust gas crossover passage is recirculated tothe induction passages.

FIG. 9 illustrates a modification of the FIG. 2 device whereby fuelmetering may be compensated for exhaust gas recirculation. The FIG. 9device is identical to that of FlG. 2, supplemented by an additional camsurface 86 on cam member 56. Concurrently with movement of control valvelever 44 by cam surface 70, cam surface 86 operates a lever 88 through acam follower 90 carried by lever 88. Lever 88 controls a unit 92 to varyan impedance which controls fuel metering as explained below.

FIG. is a schematic diagram of an electronically controlled timed fuelinjection system. As shown therein, a fuel injector '94 directs fuelinto an intake manifold runner passage 80 at the back of an inlet valve96 for a combustion chamber 98. Injector 94 is operated by a solenoid100 during each cycle of the engine, and fuel is metered by controllingthe duration of time solenoid 100 is energized to operate injector 94.

To energize solenoid 100, a signal generator 102, which nominally may beconsidered as a normally open switch, provides a negative voltage pulseduring each cycle of the engine. This pulse is differentiated by acapacitor 104 into a negative going voltage spike which is delivered tothe base 106 of a transistor 108. Transistor 108 thus ceases to conduct,and the voltage at its collector 110 increases to render a transistor112 conductive. The voltage at the collector 114 of transistor 112 thendrops and an amplifying transistor 116 stops conducting. The voltage atthe collector 118 of transistor 1 16 is thereby increased, and solenoid100 is energized to operate injector 94.

As transistor 112 starts conducting, current passes through a primarywinding 120. Primary winding 120 is coupled, through a core 122positioned by a pressure transducer 124, with a secondary winding 126.As current changes in primary winding 120, a voltage is induced insecondary winding 126 which biases base 106 of transistor 108 in anegative direction and holds transistor 108 in a nonconductive state.Over a period of time the rate of change of current in primary winding120 drops, and the voltage induced in secondary winding 126 reducessufficiently to render transistor 108 conductive and terminateenergization of solenoid 100.

In order to control the duration of time solenoid 100 is energized, unit92 may control the impedance in the circuit of either primary winding120 or secondary winding 126. Thus unit 92 could be a potentiometer 92awhich, together with resistors 128, 130 and 132, controls the currentsupplied to primary winding 120. Unit 92 also could be a switch 92bwhich adds a small resistor 134 to the resistors 136, 138, and 140controlling the bias voltage on secondary winding 126.

Asshown in P16. 9, pressure transducer 124 is responsive to the absolutepressure in induction passages 14 below throttles 16. It will beappreciated that the induction manifold pressure varies with movement ofthrottles 16 and with changes in engine load. In addition, as exhaustgas recirculation valve 36 opens and exhaust gas is recirculated toinduction passages 14, the absolute pressure in induction passages 14increases. Manifold absolute pressure transducer 124 then moves core 122in to increase the inductance between windings 120 and 126 and lengthenthe time that solenoid is energized. To compensate for this, theresistance of potentiometer 92a is increased as control valve 36 opens;this reduces the current flow through primary winding to shorten thetime that solenoid 100 is energized. Alternatively, switch 92b closesand small resistor 134 permits an increase in the bias voltage onsecondary winding 126; thus a shorter period of time is required torender transistor 108 conductive and terminate energization of solenoid100.

From the foregoing it will be appreciated that this invention provides acam mechanism for controlling exhaust gas recirculation which simplifiesvisualization and calculation of the position of the control valve, andfurther, that this invention provides a fail-safe operating mechanism inwhich the throttles are permitted to close even if the control valve orits cam mechanism were to remain open.

I claim:

1. ln an internal combustion engine having an induction passage forairflow to the engine, a throttle disposed in said induction passage androtatable between closed and open positions for controlling airflowtherethrough, an exhaust passage for exhaust gas flow from the engine,and an exhaust gas recirculation passage extending from said exhaustpassage to said induction passage for recirculating exhaust gas to saidinduction passage: a control valve mounted on a rotatable shaft in saidexhaust gas recirculation passage and controlling exhaust gas flowtherethrough, and means for operating said control valve comprising avalve lever secured to said shaft and having a cam follower portion, acam member having a straight slot formed therein, support meansextending through said slot to support said member for linear movementthereof, said member further having a cam surface along one edge thereofincluding a first valve closed portion, a first valve moving ramp, apeak valve opening portion, a second valve moving ramp, and a secondvalve closed portion, means biasing said cam follower portion of saidcontrol valve lever against said cam surface whereby said control valveis positioned in accordance with the position of said cam member, andlinking means connecting said cam member and said throttle forconcomitant movement, whereby said cam member is moved linearly as saidthrottle is rotated from closed to open position and said cam followerportion of said control valve lever successively contacts said firstvalve closed portion and said control valve remains closed, said firstvalve moving ramp and said control valve opens, said peak valve openingportion and said control valve remains open, said second valve movingramp and said control valve closes, and said second valve closed portionand said control valve remains closed, thereby proportioning the flow ofexhaust gas recirculated to said induction passage to the flow of airthrough said induction passage.

2. In an internal combustion engine having an induction passage forairflow to the engine, a throttle mounted on a rotatable throttle shaftin said induction passage controlling airflow therethrough, an exhaustpassage for exhaust gas flow from the engine, an exhaust gasrecirculation passage extending from said exhaust passage to saidinduction passage for recirculating exhaust gas to said inductionpassage, and a control valve mounted on a rotatable valve shaft in saidexhaust gas recirculation passage controlling exhaust gas flowtherethrough: means for operating said control valve comprising a cam,operating mechanism providing a one-way drive connection between saidcam and said valve shaft whereby movement of said cam in a valve openingdirection may move said valve shaft in a valve opening direction andwhereby said cam may move in a valve closing direction while saidcontrol valve remains stationary, means biasing said valve shaft in avalve closing direction, linking means providing a one-way driveconnection between said throttle shaft and said cam whereby movement ofsaid throttle shaft in a throttle opening direction may move said cam ina valve-opening direction and whereby said throttle shaft may move in athrottle-closing direction while said cam remains stationary, and meansbiasing said cam in a valve-closing direction.

1. In an internal combustion engine having an induction passage forairflow to the engine, a throttle disposed in said induction passage androtatable between closed and open positions for controlling airflowtherethrough, an exhaust passage for exhaust gas flow from the engine,and an exhaust gas recirculation passage extending from said exhaustpassage to said induction passage for recirculating exhaust gas to saidinduction passage: a control valve mounted on a rotatable shaft in saidexhaust gas recirculation passage and controlling exhaust gas flowtherethrough, and means for operating said control valve comprising avalve lever secured to said shaft and having a cam follower portion, acam member having a straight slot formed therein, support meansextending through said slot to support said member for linear movementthereof, said member further having a cam surface along one edge thereofincluding a first valve closed portion, a first valve moving ramp, apeak valve opening portion, a second valve moving ramp, and a secondvalve closed portion, means biasing said cam follower portion of saidcontrol valve lever against said cam surface whereby said control valveis positioned in accordance with the position of said cam member, andlinking means connecting said cam member and said throttle forconcomitant movement, whereby said cam member is moved linearly as saidthrottle is rotated from closed to open position and said cam followerportion of said control valve lever successively contacts said firstvalve closed portion and said control valve remains closed, said firstvalve moving ramp and said control valve opens, said peak valve openingportion and said control valve remains open, said second valve movingramp and said control valve closes, and said second valve closed portionand said control valve remains closed, thereby proportioning the flow ofexhaust gas recirculated to said induction passage to the flow of airthrough said induction passage.
 2. In an internal combustion enginehaving an induction passage for airflow to the engine, a throttlemounted on a rotatable throttle shaft in said induction passagecontrolling airflow therethrough, an exhaust passage for exhaust gasflow from the engine, an exhaust gas recirculation passage extendingfrom said exhaust passage to said induction passage for recirculatingexhaust gas to said induction passage, and a control valve mounted on arotatable valve shaft in said exhaust gas recirculation passagecontrolling exhaust gas flow therethrough: means for operating saidcontrol valve comprising a cam, operating mechanism providing a one-waydrive connection between said cam and said valve shaft whereby movementof said cam in a valve opening direction may move said valve shaft in avalve opening direction and whereby said cam may move in a valve closingdirection while said control valve remains stationary, means biasingsaid valve shaft in a valve closing direction, linking means providing aone-way drive connection between said throttle shaft and said camwhereby movement of said throttle shaft in a throttle opening directionmay move said cam in a valve-opening direction and whereby said throttleshaft may move in a throttle-closing direction while said cam remainsstationary, and means biasing said cam in a valve-closing direction.